facebook: update facebook oauth2 endpoints

Fixes #309

Change-Id: I8a97db6cb51ae6c0799adc4d171f49e77f8ec2e6
GitHub-Last-Rev: fc6fb2a0e4ff07d940ac170df47fa7d6452c860b
GitHub-Pull-Request: golang/oauth2#308
Reviewed-on: https://go-review.googlesource.com/c/127575
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
diff --git a/facebook/facebook.go b/facebook/facebook.go
index 14c801a..21c49e7 100644
--- a/facebook/facebook.go
+++ b/facebook/facebook.go
@@ -11,6 +11,6 @@
 
 // Endpoint is Facebook's OAuth 2.0 endpoint.
 var Endpoint = oauth2.Endpoint{
-	AuthURL:  "https://www.facebook.com/dialog/oauth",
-	TokenURL: "https://graph.facebook.com/oauth/access_token",
+	AuthURL:  "https://www.facebook.com/v3.1/dialog/oauth",
+	TokenURL: "https://graph.facebook.com/v3.1/oauth/access_token",
 }